The goal of this research project is the development, documentation and dissemination of a totally integrated computer-based information system (COSTAR) that supports all the medical care, financial, and administrative needs of an ambulatory care organization. The basic data capture technique is a printed encounter form containing pre-specified codes for diagnoses, medications, etc. Each practice designs such forms to meet their individual needs. The key element to COSTAR flexibility is a directory which contains the terms defined by the individual practice. All data are stored in the computer files from which are produced a variety of medical reports for patient care, quality assurance, administration, accounts receivable, and medical research. All information is available both in printed reports and also through direct access by means of terminal inquiry interaction. The system is designed in a modular fashion with sufficient flexibility to allow easy modification to meet the specific needs of different practices and to allow system extensions as the needs of the practice change over time. The system is written in the standard version of MUMPS, and is being developed in collaboration with a commercial vendor for national marketing and support.